Method and device for treating a fine-particled feedstock especially containing metal

ABSTRACT

A process for treating a finely particulate, in particular metal-containing, charge material: The charge material and a treatment gas, in particular a reduction gas, are introduced into a fluidized bed chamber of a fluidized bed reactor to form a fluidized bed. After at least partial reaction in the fluidized bed, the treatment gas is discharged from the fluidized bed and, outside the fluidized bed, is at least partially reprocessed, preferably oxidized, by an exothermic, chemical reaction with a reactant, preferably with a gaseous and/or liquid oxidizing agent. The thermal energy of this reaction is at least partially introduced into the fluidized bed chamber, in particular into the fluidized bed, or being discharged therefrom to affect the temperature of the particulate material above the bed. Also an apparatus for operating such a fluidized bed includes the chamber, lines into and out of the chamber for gas and material and a cyclone at the chamber for the material.

The invention relates to a process for treating a finely particulate, inparticular metal-containing charge material, the charge material and atreatment gas, in particular a reduction gas, being introduced into afluidized-bed chamber, for example into a fluidized-bed reactor, inorder to form a fluidized bed. The invention also relates to a unit foroperating a fluidized bed, for example a fluidized-bed reactor.

The efficiency of a fluidized-bed process can be controlled inter alia,by means of the composition of the treatment gas and by means of thetemperature in the fluidized bed.

It is known from the prior art to set the temperature of a treatment gasin a fluidized-bed process to a temperature level which is appropriatefor the particular application by means of suitable measures, forexample by admixing a cooling gas.

It is an object of the present invention to further develop a process inaccordance with the preamble of claim 1 and an apparatus in accordancewith the preamble of claim 10, making it possible to achieve aparticularly efficient and therefore economical form of the thermalinfluencing of a fluidized-bed process.

According to the invention, this object is achieved by the processaccording to the invention described in the characterizing clause ofclaim 1 and the apparatus according to the invention described in thecharacterizing clause of claim 10.

The proposed process is particularly suitable for the treatment, inparticular the reduction of a finely particulate metal oxide, inparticular a finely particulate iron oxide. However, the invention isnot restricted to this particular application, and consequently allstatements made in connection with the reduction are to be consideredpurely as examples.

These specific statements also apply, with appropriate modificationswhich it will be possible for the person skilled in the art to perform,to all other, in particular equivalent industrial treatments in which afluidized-bed process is employed. By way of example, the invention mayalso be employed in the cement industry.

According to a particular embodiment of the process according to theinvention, the fluidized bed forms in a partial section, in particularin a lower partial section, of the fluidized-bed chamber, and/or the atleast partially reacted treatment gas is reprocessed within thefluidized-bed chamber, preferably above the fluidized bed, and/or the atleast partially reprocessed treatment gas is discharged from thefluidized-bed chamber, preferably above the fluidized bed.

According to a particular embodiment of the process according to theinvention, a device for reprocessing the treatment gas which has atleast partially reacted in the fluidized bed, for example an oxygenburner and/or a oxygen nozzle, is operated in the fluidized-bed chamberabove the fluidized bed, with thermal energy being generated or consumedduring the at least partial reprocessing, in particular during an, ifappropriate exothermic, oxidation, of the treatment gas.

According to a preferred embodiment of the process according to theinvention, the thermal energy is generated or consumed above thefluidized bed in the fluidized-bed chamber.

According to a preferred embodiment of the process according to theinvention, thermal energy which is generated or consumed above thefluidized bed is introduced into the fluidized-bed chamber above thefluidized bed or removed from the fluidized-bed chamber above thefluidized bed.

According to a preferred embodiment of the process according to theinvention, an oxidizing agent, for example oxygen and/or air, isintroduced directly into the fluidized-bed chamber above the fluidizedbed, if appropriate via the device for reprocessing the treatment gaswhich is arranged above the fluidized bed in the fluidized-bed chamber,for the purpose of reprocessing the treatment gas.

According to a preferred embodiment of the process according to theinvention, the at least partially reacted treatment gas, in particularreduction gas, is at least partially burnt, in particular at leastpartially oxidized, in the fluidized-bed chamber above the fluidizedbed, if appropriate by the device for reprocessing the treatment gaswhich is arranged above the fluidized bed in the fluidized-bed chamber.

A combustion represents, for example, a chemical reaction in order toobtain thermal energy, for example an exothermic oxidation.

According to a preferred embodiment of the process according to theinvention, finely particulate charge material which emerges from thefluidized bed and is in particular at least at times located above thefluidized bed is at least partially heated and/or cooled, if appropriateby the treatment gas, which is guided above the fluidized bed in thefluidized-bed chamber and has been at least partially reprocessed, inparticular burnt and/or oxidized and/or heated, and/or by the device forreprocessing the treatment gas itself.

According to a particular embodiment of the process according to theinvention, a cyclone is arranged in the fluidized-bed chamber above thefluidized bed, the finely particulate charge material being heated orcooled in the region of the cyclone, in particular of the cyclone inlet,by the treatment gas, which is guided above the fluidized bed in thefluidized-bed chamber and has been at least partially reprocessed, inparticular oxidized and/or heated, and/or by the device for reprocessingthe treatment gas itself.

According to a particular embodiment of the process according to theinvention, the finely particulate charge material, which is situatedabove the fluidized bed and has been heated or cooled, is at leastpartially introduced into the fluidized bed, in particular recycled.

Furthermore, the invention is characterized by an apparatus as describedin claim 10, preferably for carrying out the process as claimed in oneor more of claims 1 to 9.

According to a preferred embodiment of the apparatus according to theinvention, the device for reprocessing the treatment gas which isarranged in the fluidized-bed chamber above the fluidized bed isdesigned to introduce a liquid and/or solid combustion agent, preferablyan oxidizing agent and/or an oxygen carrier, particularly preferablyoxygen and/or air, into the fluidized-bed chamber.

According to a preferred embodiment of the apparatus according to theinvention, the device for reprocessing the treatment gas which isarranged above the fluidized bed in the fluidized-bed chamber isarranged in the region of the splash zone, so that the finelyparticulate charge material which is present in the region of the splashzone can be at least partially heated and/or cooled by the device itselfand/or by the at least partially reprocessed, in particular oxidizedand/or heated, treatment gas.

In this context, the splash zone characterizes that part of the freespace above the fluidized bed in which fine and solid particles arethrown up and then at least partially dropped back into the fluidizedbed.

According to a particular embodiment of the apparatus according to theinvention, the unit has a cyclone which is arranged above the fluidizedbed in the fluidized-bed chamber, a dipleg which extends into thefluidized bed adjoining the cyclone outlet if appropriate, and,furthermore, the device for reprocessing the treatment gas which isarranged above the fluidized bed in the fluidized-bed chamber beingarranged at the level of the cyclone, in particular the cyclone inlet,and it being possible for the finely particulate charge material, in theregion of the cyclone, in particular of the cyclone inlet, to be atleast partially heated or cooled by the device itself and/or by the atleast partially reprocessed, in particular oxidized, heated treatmentgas.

According to a particular embodiment of the invention, a diplegrepresents a device for returning material which has been separated outin a cyclone into a fluidized bed.

In various fluidized-bed reduction processes, the charge ore is heatedand reduced in countercurrent in 3 to 4 fluidized-bed reactors. In thisapplication, the temperature profile is set by means of the heat contentof the reduction gas and the heats of reaction.

Therefore, the thermal budget process management of a correspondingprocess can be altered only within narrow limits.

The prior art has disclosed external preheating of the reduction gas,but this has proven uneconomical. The partial combustion of reductiongas upstream of the fluidized bed has an adverse effect on the reductionpotential of the reduction gas and therefore on the reduction work whichcan be achieved.

Extensive tests relating to the use of burners, in particular of oxygenburners, in fluidized-bed units have shown that slag formations whichdestabalize the fluidized-bed process generally occur in the region ofthe flame on account of the high particle concentration in thefluidized-bed unit. Moreover, in this region reliable flame monitoringand ignition assistance are very difficult to realize.

The present invention optimizes the energy budget, in particular theintroduction of energy.

According to the process according to the invention, in a particularembodiment of the invention, at least one oxygen burner is arrangedabove the fluidized bed in order to increase the fluidized-bedtemperature. Compared to conventional burners, the oxygen burneraccording to the invention is distinguished by the fact that thecombustion, in particular the oxidation, of the treatment gas, inparticular of the reduction gas, takes place upstream of the oxygenburner, as early as in the fluidized-bed chamber. In its most simpleembodiment, the oxygen burner represents a nozzle for feeding an oxygencarrier into the fluidized-bed chamber.

According to a particular embodiment of the process according to theinvention, the term oxygen carrier by definition encompasses alloxygen-containing substances and all substances which provide and/orrelease oxygen under the ambient conditions prevailing in thefluidized-bed chamber for at least partial oxidation of the treatmentgas and/or of the finely particulate charge material, i.e. in particularpure oxygen and/or air.

According to a particular embodiment of the invention, as a result ofthe particles being thrown up out of the fluidized bed, the particlesare heated in the free space above the fluidized bed by the oxygenburner and then dropped back into the fluidized bed.

According to a particular embodiment of the invention, the particles ordust, which is heated further, are separated out at an optional cycloneand then returned to the fluidized bed again.

Unlike with the concept of the gas heating upstream of the fluidizedbed, according to a particular embodiment of the invention with theproposed arrangement, the reduction potential of the reduction gas onlydeteriorates downstream of the fluidized bed. This makes it possible tomake use of the reduction potential of the gas at an elevated bedtemperature. A high gas temperature when the working gas enters thereactor is prevented. This counteracts the known problems of cakingoccurring at the distributor bases.

Furthermore, the risk of slag formation (caking) occurring in the regionof the fluidized bed or the fluidized-bed chamber is reduced by thelower particle concentration in the region of the flame.

The following particular advantages can be realized by the subjectmatter of the invention:

-   -   efficient and simple flame monitoring and ignition assistance    -   better and more uniform treatment, in particular reduction, on        account of the increase in the fluidized-bed temperature while        maintaining an approximately constant quality of treatment gas    -   efficient and simple influencing of the temperature profile of        the fluidized bed    -   longer service lives of the distributor base    -   higher productivity resulting from improved efficiency of the        fluidized-bed process.

The proposed invention has proven particularly efficient when it isemployed in a process with a plurality of fluidized beds operated inparallel and/or in series, since in this case the individual fluidizedbeds can be particularly flexible matched to one another in terms of thetemperatures employed.

According to a particular embodiment of the invention, it is possiblefor the fluidized-bed reaction, for example the reduction of the finemetal oxide, to be carried out in the fluidized bed prior to the furtherreprocessing of the treatment gas, for example partial combustion, yetnevertheless to control the temperature in the fluidized bed, inparticular by means of recycled particles, preferably of the finelyparticulate charge material.

According to particular embodiments of the invention, the recycling iseffected on the one hand by cyclone recycling, for example via a dipleg,and/or on the other hand by the particles which have been thrown out ofthe fluidized bed dropping back into it. According to these embodiments,heating of the fluidized bed is achieved without the treatment gas beinginfluenced before or during the reaction in the fluidized bed.

The invention is explained below, in accordance with a particular,non-limiting embodiment, on the basis of a diagrammatic drawing, inwhich:

FIG. 1 shows a process for treating a finely particulate, in particularmetal-containing, charge material

FIG. 1 shows a unit 1 for operating a fluidized bed, for example afluidized-bed reactor, which has a wind chamber 2 and a fluidized-bedchamber for holding a fluidized bed 4 and a free space 5. Furthermore,the unit 1 has a distributor base 3 for distributing the treatment gas6, in particular a reduction gas.

A finely particulate charge material, in particular iron oxide, is fedto the unit 1 via a line 8, and is removed again, in at least partiallytreated form, via a line 9.

In the unit 1 there is a cyclone 10 and a dipleg 11, which is used toseparate out the dust or fine charge material and recycle it into thefluidized bed 4. As is known to the person skilled in the art, thefluidized bed 4 behaves similarly to a boiling liquid and is delimitedat the top by a defined, albeit blurred, surface which isdiagrammatically depicted in the FIGURE. Immediately above this blurredboundary is what is known as the splash zone, which is distinguished bythe occurrence of fine particles therein, which are thrown up out of thefluidized bed and then dropped back into it.

In the fluidized-bed chamber there is an oxygen burner 12 for feedingoxygen 11 into the fluidized-bed chamber above the fluidized bed 4.According to a particular embodiment, the oxygen burner itself islocated in the splash zone (as illustrated in FIG. 1) or at any rate isused to introduce heat directly into the splash zone. A particle 16 isheated by the oxygen burner 12 in the splash zone before dropping backinto the fluidized bed, thereby making a contribution to the heating ofthe latter.

According to a further embodiment of the invention, a burner 14 forsupplying an oxygen carrier 15 is provided in the region of the cyclone10, in particular of the cyclone inlet.

In this way, treatment gas is burned in the fluidized-bed chamber andheat is generated above the fluidized bed 4, this heat being useddirectly to heat the fluidized bed 4 (or to heat it through), forexample by means of the solid particles which have been separated out inthe cyclone 10 through the dipleg 11.

By way of example the arrow 17 sketches the path of a fine solidparticle out of the fluidized bed 4 via the splash zone into the freespace 5, this particle being correspondingly heated by the oxygen burner14 and then recycled into the fluidized bed 4 via the cyclone 10 and thedipleg 11.

The at least partially reacted treatment gas is discharged again via aline 7.

1-10. (Canceled)
 11. A process for treating a finely particulate chargematerial, the method comprising: introducing the charge material and atreatment gas into a fluidized bed chamber and there forming a fluidizedbed, wherein a cyclone is arranged in the fluidized bed chamber abovethe fluidized bed; at least partially reacting the treatment gas in thefluidized bed, then discharging the treatment gas from the fluidized bedto outside the fluidized bed; at least partially reprocessing theexited, at least partially reacted treatment gas in a chemical reactionwith a reactant in a device for reprocessing the treatment gas, andoperating the device for reprocessing in the fluidized bed chamber abovethe fluidized bed and there producing thermal energy from the chemicalreaction; at least partially introducing the thermal energy into thefluidized bed chamber or discharging the thermal energy from thefluidized bed chamber, wherein the finely particulate charged materialis heated or cooled in the region of the cyclone by the treatment gasabove the fluidized bed in the fluidized bed chamber which gas has beenat least partially pre-processed and had its temperature affected. 12.The process of claim 11, wherein the treatment gas is a reduction gasintroduced into the fluidized bed chamber and the fluidized bed chamberis a fluidized bed reactor.
 13. The process of claim 12, wherein the atleast partial reprocessing of the treatment gas comprises oxidizing thetreatment gas in an exothermic chemical reaction with a reactantcomprised of at least one of a gaseous or a liquid oxidizing agent. 14.The process of claim 13, wherein the device for reprocessing thetreatment gas is at least one of an oxygen burner or an oxygen nozzleand the device for reprocessing is operable in the fluidized bed chamberabove the fluidized bed and generating thermal energy, and at leastpartially introducing the thermal energy of the reprocessing device intothe fluidized bed or partially discharging the thermal energy forheating or cooling the finely particulate charge material in the regionof an inlet to the cyclone, wherein the thermal energy of the chemicalreaction is introduced into the fluidized bed by guiding the treatmentgas, which has been at least partially pre-processed, into the fluidizedbed chamber above the fluidized bed.
 15. The process of claim 14,wherein the finely particulate charge material is heated or cooled inthe region of the cyclone inlet by either the treatment gas or by thedevice for reprocessing the treatment gas.
 16. The process of claim 13,wherein the finely particulate charge material is a metal-containingcharge material.
 17. The process of claim 13, wherein the fluidized bedforms in a lower partial section of the fluidized bed chamber, and theprocess further comprising reprocessing the at least partially reactedtreatment gas within the fluidized bed chamber above the fluidized bed,and the discharging of at least partially reprocessed treatment gas isfrom the fluidized bed chamber above the fluidized bed.
 18. The processof claim 17, wherein the thermal energy is generated or consumed abovethe fluidized bed in the fluidized bed chamber.
 19. The process of claim17, further comprising introducing an oxidizing agent into the fluidizedbed chamber above the fluidized bed for reprocessing the treatment gas.20. The process of claim 19, wherein the oxidizing agent is introducedby a device for reprocessing the treatment gas arranged above thefluidized bed in the fluidized bed chamber.
 21. The process of claim 19,wherein the oxidizing agent is oxygen or air.
 22. The process of claim12, wherein the at least partially reacted treatment gas is at leastpartially oxidized in the fluidized bed chamber above the fluidized bed.23. The process of claim 22, wherein the at least partially reactedtreatment gas is at least partially oxidized by a device forreprocessing the treatment gas arranged above the fluidized bed in thefluidized bed chamber.
 24. The process of claim 11, wherein thefluidized bed is operable for causing finely particulate charge materialto emerge from the fluidized bed and at least at times to be above thefluidized bed, then heating or cooling the material above the fluidizedbed by at least one of the treatment gas which is guided above thefluidized bed in the fluidized bed chamber and which has been partiallyreprocessed or by the device for reprocessing the treatment gas.
 25. Theprocess of claim 24, further comprising at least partially introducinginto the fluidized bed the finely particulate charge material which isabove the fluidized bed and has been heated or cooled there. 26.Apparatus for operating a fluidized bed for treating a finelyparticulate charge material, the apparatus comprising; a distributorbase operable for distributing a treatment gas; a fluidized bed chamberdefines the fluidized bed above the base, the fluidized-bed chamberhaving a lower region in which the fluidized bed is disposed; thefluidized bed chamber being operable for reprocessing treatment gas inthe fluidized bed chamber above the fluidized bed; a first line forsupplying a finely particulate fluidizable charge material, a secondline for discharging treated charge material from the chamber; a thirdline for introducing treatment gas to the chamber and a fourth line fordischarging treatment gas from the chamber; a cyclone in the fluidizedbed chamber arranged above the fluidized bed, the cyclone having anoutlet therefrom into the fluidized bed; a dipleg extending into thefluidized bed and adjoining the cyclone outlet, a device forreprocessing at least partially reacted treatment gas of the fluidizedbed, the reprocessing device being located in the fluidized bed chamberabove the fluidized bed and the reprocessing device being operable forintroducing thermal energy to or discharging the thermal energy from thefluidized bed, the reprocessing device being positioned above thefluidized bed in the fluidized bed chamber at the level of the cycloneenabling the finely particulate charge material then in the region ofthe cyclone to be heated or cooled by the reprocessing device or by theat least partially reprocessed treatment gas.
 27. The apparatus of claim26, wherein the charge material in the fluidized bed is a finelyparticulate metal-oxide and the treatment gas is a reduction gastherefor.
 28. The apparatus of claim 26, wherein the cyclone has aninlet located in the fluidized bed chamber and also located such thatthe finely particulate charge material is heated or cooled in the regionof the cyclone inlet.
 29. The apparatus of claim 27, wherein the devicefor reprocessing the treatment gas in the fluidized bed chamber abovethe fluidized bed is operable to introduce a liquid or a solid oxidizingagent into the fluidized bed chamber.
 30. The apparatus of claim 29,wherein the oxidizing agent is oxygen or air.
 31. The apparatus of claim26, wherein there is a splash zone for the particulate material at thefluidized bed caused by the operation of the fluidized bed; the devicefor reprocessing treatment gas is arranged above the fluidized bed inthe fluidized bed chamber in the splash zone of the fluidized bed forcausing heating or cooling of the charge material in the splash zone bythe reprocessing device or by the at least partially reprocessedtreatment gas.